For human and animal single photon emission computed tomography (SPECT) imaging, anesthesia and physical restraints may be used to reduce or eliminate motion, however these methods may directly influence the pharmacokinetics of the relevant biological system or cause stress that may indirectly affect radiotracer uptake and retention. These effects are pronounced in brain scanning. Imaging unanesthetized, unrestrained small animals can provide unique capabilities for biomedical research by eliminating the impact of anesthetic on the animal brain function and reducing the stress to the animal, thus opening new possibilities in the area of brain studies.
Conventional image reconstruction for emission computed tomography assumes that the source activity distribution and the human, animal or object being imaged are static. This assumption is not necessarily true for human imaging, where there may be some head or body motion, for imaging unanesthetized animals where the animal may be in motion, or for imaging plants where there may be motion due to the wind or mechanical disturbances. Image reconstruction without motion compensation results in blurred and degraded images, which affects the interpretation and quantitative measurement of radiotracer distribution. Smaller regions of radionuclide accumulation are more difficult to discern. For biological imaging this degradation due to motion influences the measurement of physiological parameters from the radiotracer biodistribution. It would be of great benefit to provide a system for imaging such moving objects, humans and animals, without these blurring artifacts.